This invention relates to a system and product for reinforcing structural elements and a method for attaching the product to those structures. In particular, the invention includes strips of carbon fiber material designed for adherence to a structural element such as a cinder or concrete block wall.
Walls constructed of concrete blocks are well known in the field of construction and have been extensively used for walls both above and below ground. Walls constructed in this manner are generally capable of supporting residential and light commercial structures and are relatively inexpensive to manufacture.
In order to construct a concrete wall, individual blocks are laid end to end and successive rows or courses are stacked thereon. Mortar between each adjacent block and row secures the wall together These walls are such that they have excellent compressive strength to support structures placed upon them. However, these walls are inherently weak with respect lateral loads and are particularly susceptible to cracking from water pressure. This inherent weakness is attributable to the structural characteristics of the walls themselves and the mortar joints at which they are connected. Specifically, the mortar joints are weak in tension, and when subjected to tensile forces, tend to separate relatively easily.
Water penetrating deeply into the soil adjacent a basement wall can cause substantial lateral movement of the soil and pressure against a wall. Over a period of time, block walls may be seen to develop diagonal cracks at their ends and vertical cracks near their centers. Such cracks can admit water from the surrounding soil and, if left untreated, can progressively widen and eventually facilitate collapse of the entire wall with resultant damage to the structure supported on it. In addition to developing such cracks, under such pressure block walls typically either tilt or bow inwardly and such bowing or tilting steadily worsens with the weight of the overlying structure.
One of the traditional methods of repairing the leaks and cracks and relieving the external pressure is to drill holes and provide for channeling of the water away on the inside. Yet another method is to fill the cracks and leaks is by injection of an epoxy resin into the cracks. Although these methods will control or prevent further water from entering the existing cracks, they do not bind the concrete walls and prevent further cracking or bowing of the concrete walls.
Yet another means of correcting the cracks in the walls is to use fiberglass cloth with epoxy or polyester resin. Fiberglass has good tensile properties and can carry the load on the interior of the basement walls that is in tension. However, one of the major drawbacks with this method is that mixing the epoxy or polyester and wetting out the fabric is time consuming and messy.
In recent years, technology has developed whereby the concrete walls are reinforced using precut strips of carbon fiber. This prevents the walls from cracking or collapsing. However, precut carbon fiber strips have to be cleaned and roughened, commonly done through sanding, to provide mechanical adhesion with the walls. The sanding process is not only time consuming, but is completely dependent on the skill of the operator in sanding the surface of the strip. This results in extra cost in transporting and storing the precut strips.
With the limitations of the prior art in mind, it is an object of the present invention to provide an article for reinforcing a structure element to effectively resist bending or other lateral forces applied to the structure element.
Another object of the present invention is to provide an article that does not require any sanding to enhance mechanical adhesion in order to attach to the article to the structural element and one which will remain sufficiently clean at a job site.
It is yet another object of the present invention to provide a method whereby an article for use in reinforcing is firmly adhered to the structural element, thereby reinforcing the structural member.
It is yet another object of the present invention to use existing materials to apply uniform pressure to firmly adhere the article to the structural element, thereby resulting in a strong reinforced structural element.
Another object of the present invention is to provide an article and method which is economical, efficient in operation, capable of a long operating life.
In accordance with the preferred embodiment of the present invention, an article (a reinforcing member) and method for reinforcing structural elements, such as concrete walls, support beams and the like, are provided.
The article in accordance with the present invention comprises a carbon fiber strip with an exposed roughened surface. In order to make the article, epoxy resin is applied to a carbon fibers. The epoxy resin is allowed to permeate the thickness of the carbon fibers. Due to the uneven surface of the carbon fibers, a thin layer of epoxy forms on a top or exterior of the carbon fiber. A plastic cover sheet is then placed on top of the carbon fiber. Carbon fiber material with the epoxy and the plastic fiber is then subject to high heat and pressure to cure the epoxy thereby forming the carbon fiber into a rigid sheet, with an adhered cover sheet, that can be cut into strips. At the job site, the cover sheet is readily removed and resultant sheet of carbon fiber will have a roughened surface defined by the epoxy resin where it had adhered to the cover sheet.
The method of adhering the product to a structural element comprises the steps of applying a second epoxy resin to the structural element; adhering the product to the second epoxy resin; allowing the second resin to cure while applying pressure to the article and structural element. Pressure may be applied through use of an overlying plastic sheet, the edges of which are sealed with the help of an adhesive to the structural element. A uniform pressure is applied with the help of an external vacuum pump and the vacuum is applied until the epoxy is cured and the product firmly fixed to the structural element.